Solid propellant compositions containing plasticized nitrocellulose and aluminum hydride

ABSTRACT

1. A solid propellant composition consisting essentially of a cured intimate mixture of from about 5% to about 25% by weight powdered aluminum hydride; from about 30% to about 70% by weight of an oxidizing agent selected from the group consisting of ammonium perchlorate, sodium perchlorate, potassium perchlorate, ammonium nitrate, potassium nitrate, and sodium nitrate; and from about 15% to about 70% by weight of plasticized nitrocellulose.

United States Patent [191 Huskins et al.

[ 51 Aug. 28, 1973 1 SOLID PROPELLANT COMPOSITIONS CONTAINING PLASTICIZED NITROCELLULOSE AND ALUMINUM HYDRIDE [75] Inventors: Chester W. Huskins, Huntsville,

laiti iyn -flanetqrfiyl slstm Tenn.; Orval E. Ayers, Huntsville, Ala.

[73] Assignee: The United States of America as represented by the Secretary of the Army, Washington, DC.

[22] Filed: Mar. 13, 1963 [21] Appl. No.: 265,592

[52] U.S. Cl. 149/18, 149/19, 149/20, 149/38, 149/96 [51 1 IntrCl C06d 5/06 [58] Field 01 Search 149/17, 18, 19, 38, 149/96, 3, 118, 275

[ 56] r 5 References Cited UNITED STATES PATENTS 2,992,908 7/1961 Hedrick et a1. 149/22 3,107,185 10/1963 Hedi'ick et a1. 149/19 X 3,035,948 5/1962 Fox 149/19 3,053,709 9/1962 Herty 149/19 3,083,526 4/1963 Hudson l49/19 X 3,046,829 7/1962 Roemer 149/19 X Primary Examiner-Benjamin R. Padgett Attorney-Harry M. Saragovitz, Edward .1. Kelly, Herbert Bet! and Jack Voigt EXEMPLARY CLAIM 5 Claims, No Drawings SOLID PROPELLAN'I COMPOSITIONS CONTAINING PLASTICIZED NITROCELLULOSE AND ALUMINUM HYDRIDE The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.

This invention relates to solid propellant compositions. In one aspect, the invention relates to improving the performance of solid propellant compositions by incorporating powdered aluminum hydride therein as a high energy fuel. In another aspect, the invention relates to specific solid propellant compositions containing powdered aluminum hydride as a fuel.

Solid propellant compositions are utilized extensively as rocket propellants, especially in military rockets. There is, therefore, a great emphasis on perfecting solid propellants to obtain greater thrust. One approach toward perfecting solid propellant performance has been through the addition of high energy metallic fuel to solid compositions. Among the metals which have found use as high energy fuels are beryllium, boron, aluminum, and magnesium.

It has now been determined that powdered aluminum hydride is an excellent fuel for solid propellants.

The principal object of this invention is, therefore, to provide an improvement in solid propellant compositions by substituting powdered aluminum hydride for all or part of the metallic fuels previously used.

Another object of this invention is to provide particular solid propellant compositions containing powdered aluminum hydride as the fuel.

. The manner in which these and other objects may be accomplished will become apparent to those skilled in the art from the detailed description which follows.

The aluminum hydride utilized in the invention is available as a powder of varying average particle sizes. Olane 58 manufactured by Olin 'Mathieson Chemical Companyand Dow 1451 manufactured-by Dow Chemical Company are illustrative of the type of aluminum hydride contemplated by the invention, both of these hydrides being identical to each other as shown by their X-ray diffraction pattern. These hydrides exhibit a peak of 5.8 microns in the infrared spectrum. The use of stabilized aluminum hydride is also contemplated by the invention, such as mercury stabilized aluminum hydride.

For the purposes of this invention, aluminum hydride having an average particle size of 25 microns to 300 microns should be utilized. This limitation is imposed by the bulk density of aluminum hydride itself. Very small particles absorb large quantities of the liquid ingredients during the mixing of the composition and thus limit the amount of aluminum hydride which can be incorporated into the composition. The use of larger particles greatly relieves this problem. However, notwithstanding the limitations imposed by the mixing techniques, it should be obvious that powdered aluminum hydride having an average particle size of less than one micron up to 300 microns or larger could be utilized.

Aluminum hydride proved to be compatible with those substances normally found in solid propellant compositions. Examples of substances with which aluminum hydride proved to be compatible are acrylonitrile, CTL polymer of Phillips Petroleum Company, methyl azirdinyl phosphinyl oxide, diethylene glycol dinitrate, EPON 812 polymer, nitroglycerin, triacetin,

l,2,3-tris(difluoroamino) propane, 2,3- bis(difluoroamino) propyl formate, acetic anhydride, allyl alcohol, allyl acetate, triethylene glycol dinitrate,

l,2,3-tris(difiuoroamino) propane, and 2,3- bis(difluoroamino) propyl formate.

Basically, the propellant compositions contemplated within the scope of the invention consist of powdered aluminum hydride, an oxidizer, and a binder. Of course, aluminum hydride can be utilized in combination with the other metallic fuels such as aluminum and need not be the only metal component in the compositions.

Any of the commonly used inorganic oxidizers per forms satisfactorily. The chlorates, perchlorates, chromates, and dichromates are acceptable as oxidizers. Particularly, ammonium perchlorate, sodium perchlorate, potassium perchlorate, ammonium nitrate, potassium nitrate, and sodium nitrate are useful in compositions comprising aluminum hydride as a fuel. of these, ammonium perchlorate is preferred.

' Binders for use in propellant compositions are well known in the art. Among the commonly used binders are the polysulfide polymer, polyurethanes, GR-S, neoprene, plasticized nitrocellulose, copolymers of butadiene and acrylic acid, and the like. Particularly useful as a binder in the present invention is the copolymer of polybutadiene and acrylic acid or plasticized nitrocellulose. The binder serves as a fuel itself and sufficient oxidizer should be utilized in the composition to assure complete combustion of the binder for maximum fuel performance. Since the binder material itself may contain available oxygen, it is not necessary that all of the oxygen for burning the binder come from the oxidizer.

.In the case of the plasticized nitrocellulose, there is ordinarily more than enough available oxygen within the binder to assure complete combustion of the binder.

It should be kept in mind that depending on the binder employed, small amounts of curing agents and- /or accelerators may be necessary to accomplish the curing process. For example, with the polysulfides, p-

'quinone dioxime is used as a curing agent and diplenylguanidine is employed as an accelerator. In the event that the propellant'is to be subjected to prolonged storage, stabilizers can be added. With plasticized nitrocellulose, resorcinol serves as a stabilizer. Curing agents, accelerators, and stabilizers are considered herein as being a part of the binder. Thus, when the percentage by weight of binder if referred to with regard to the composition, the percentage is inclusive of whatever curing agents, accelerators, or stabilizers, if any, are utilized in obtaining a cured binder.

The composition of the invention can vary considerably with regard to the ratio of constituents. Generally. the powdered aluminum hydride will comprise about 5% to 25% by weight of the total composition. The greater the aluminum hydride content, the more hydrogen-rich is the fuel. Thus, the aluminum hydride furnishes hydrogen to readily react with any available oxidizer and thereby increase the thrust. The binder, including curing agents, accelerators, and stabilizers, makes up about 15% to by weight of the composi tion. The oxidizing agent varies from 20% to 70% by weight of the composition.

The actual manufacture of the propellant compositions is done using standard apparatus and techniques.

The necessary materials are thoroughly mixed either manually or with conventional mixing devices such as a Baker-Perkins dispersion blade mixer. After mixing, the material is placed in a mold of the desired shape or any other suitable container and allowed to stand until cured. The application of mild heat accelerates the curing process. Because heat tends to decompose aluminum hydride, the temperature should not be allowed to exceed 140 F.

Once cured, the propellant is placed in a conventional reaction motor and fired with ordinaryligniters such as those presently in widespread use with military rockets. In many cases the propellant will be placed within the walls of the rocket motor prior to curing so that upon curing the solid propellant is already in place.

Actual examples of propellant compositions representative of the type encompassed by the invention are presented below.

EXAMPLE I A propellant composition comprising the following ingredients is prepared as indicated hereinafter:

Percent INGREDIENT Weight weight Fluid ball powder nitrocellulose (12.6%N) 9.35 g. 18.85 Triethyleneglycol dinitrate 20.95 g. 42.24 Resorcinol 0.50 g. 1.00 Ammonium Perchlorate 15.00 g. 30.24 Aluminum Hydride 3.80 g. 7.66

"Olin Mathieson product identified as X-1537 EXAMPLE II A propellant composition comprising the following ingredients is prepared as described below:

Percent INGREDIENT Weight by Weight Polybutadiene-acrylic acid liquid copolymer 8.62 g. 19.68 EH. 2774 (curing agent) 1.18 g. 2.69 Ammonium perchlorate 30.00 g. 68.49 Aluminum hydride 4.00 g. 9.13

" Difuncional epoxide produced by Union Carbide Chemical Co.

The acrylic acid-butadiene mixture and the ERL 2774 curing agentare thoroughly mixed and placed in the oven at 140 F. and allowed to warm for about 30 minutes. Ammonium perchlorate is then added with mixing. Finally, aluminum hydride is added and all the ingredients again thoroughly mixed. The propellant mixture is then placed in a mold and allowed to cure for 4 days at F.

The above examples are for the purpose of illustration only. It is readily apparent that the invention lends itself to widespread application. Conventional solid propellants presently in use which employ other metallic derivatives as fuels come within the scope of the invention merely by substituting aluminum hydride for all or part of the metallic fuel now in use. No change in the method of preparation is necessitated by this substitution other than regulation of the temperature at F. or below. Moreover, many other new solid propellants can be prepared using aluminum hydride as a fuel merely by following the instructions given hereinabove.

The use of aluminum hydride in solid propellant compositions of the invention offers the advantage of an excellent hydrogen-rich fuel source which can be utilized to achieve greater thrust in rocket engines.

No undue limitation of the invention is intended by the detailed description thereof except as reflected in the appended claims.

We claim:

1. A solid propellant composition consisting essentially of a cured intimate mixture of from about 5% to about 25% by weight powdered aluminum hydride; from about 30% to about 70% by weight of an oxidizing agent selected from the group consisting of ammonium perchlorate, sodium perchlorate, potassium perchlorate, ammonium nitrate, potassium nitrate, and sodium nitrate; and from about 15% to about 70% by weight of plasticized nitrocellulose.

2. A composition according to claim 1 wherein said oxidizing agent is ammonium perchlorate.

3. A solid propellant composition consisting essentially of a cured intimate mixture of about 8% powdered aluminum hydride, about 19% nitrocellulose, about 42% plasticizer for said nitrocellulose, about 1% of a stabilizer for nitrocellulose, about 30% of an inorganic oxidizer selected from the group consisting of ammonium perchlorate, sodium perchlorate, potassium perchlorate, ammonium nitrate, potassium nitrate, and sodium nitrate wherein all percentages refer to per cent by weight of total composition.

4. A composition according to claim 3 wherein said plasticizer for 'said nitrocellulose is triethyleneglycol dinitrate and said oxidizer is ammonium perchlorate.

5. A composition consisting essentially of a cured intimate mixture of the following:

INGREDIENT BY WEIGHT Nitrocellulose (12.6%N) 18.85 Triethyleneglycol Dinitrate' 42.24 Resorcinal 1.00 Ammonium Perchlorate 30.24 Aluminum Hydride 7.66 

1. A SOLID PROPELLANT COMPOSITION CONSISTING ESSENTIALLY OF A CURED INTIMATE MIXTURE OF FROM ABOUT 5% TO ABOUT 25% BY WEIGHT POWDED ALUMINUM HYDRIDE, FROM ABOUT 30% TO ABOUT 73% BY WEIGHT OF AN OXIDIZING AGENT SELECTED FROM THE GROUP CONSISTIN OF AMMONIUM PERCHLORATE, SODIUM PERCHLORATE, POTASSIUM PERCHLORATE, AMMONIUM NITRATE, POTASSIUM NITRATE, AND SODIUM NITRATE, AND FROM ABOUT 15% TO ABOUT 70% BY WEIGHT OF PLASTICIZED NITROCELLULOSE.
 2. A composition according to claim 1 wherein said oxidizing agent is ammonium perchlorate.
 3. A solid propellant composition consisting essentially of a cured intimate mixture of about 8% powdered aluminum hydride, about 19% nitrocellulose, about 42% plasticizer for said nitrocellulose, about 1% of a stabilizer for nitrocellulose, about 30% of an inorganic oxidizer selected from the group consisting of ammonium perchlorate, sodium perchlorate, potassium perchlorate, ammonium nitrate, potassium nitrate, and sodium nitrate wherein all percentages refer to per cent by weight of total composition.
 4. A composition according to claim 3 wherein said plasticizer for said nitrocellulose is triethyleneglycol dinitrate and said oxidizer is ammonium perchlorate.
 5. A composition consisting essentially of a cured intimate mixture of the following: INGREDIENT % BY WEIGHT Nitrocellulose (12.6%N) 18.85 Triethyleneglycol Dinitrate 42.24 Resorcinal 1.00 Ammonium Perchlorate 30.24 Aluminum Hydride 7.66 